In conventional deinking procedures, the paper is mechanically pulped and contacted with an aqueous medium containing a deinking chemical. The pulping and presence of the deinking chemical results in a separation of the ink from the pulp fibers and the dispersed ink is then separated from the pulp fibers by washing or flotation processes.
Increasing amounts of printed paper are being generated today from electrophotographic processes such as xerography and non-impact printing processes such as laser and ink-jet printing. Deinking processes capable of deinking these types of printed paper are very complex and are capital intensive. In addition, multiple steps are required for debris removal and actual ink removal. Generally, ink removal procedures involve washing, flotation, forward cleaning and high consistency dispersion to reach the level of speck removal and brightness required in the deinked pulp to produce recycled paper.
As an alternative to conventional deinking procedures, the prior art has shown use of agglomeration deinking processes. Agglomeration chemicals consisting of polymeric systems are employed to aid in the ink agglomeration process. In deinking paper through agglomeration the waste paper is repulped and deinked through chemical treatment to provide a slurry of pulp and ink agglomerates. The ink agglomerates are removed from the pulp through a variety of separation procedures.
U.S. Pat. No. 4,013,505 to Balcar et al. discloses a method of deinking printed wastepapers by impregnating the wastepaper with surface active agents so that upon repulping the ink particles are released from the paper fibers. Adsorptive flakes comprised of solutions of metal soaps of fatty acids are added to the repulped paper stock to cause precipitation of the separated ink particles. The adsorptive flakes containing printing ink are separated from the repulped paper stock by latent vortex action.
U.S. Pat. No. 4,076,578 to Puddington et al. discloses a method for deinking wastepaper, particularly newsprint, in which ink coated solids are removed by physical means such as hydrocyclones, screens or decantation.
The methods in Balcar and Puddington provide processes which require the use of expensive deinking agents and involve complex process steps to remove ink particles to produce a relatively clean paper stock.
Therefore, known deinking processes are not entirely satisfactory in that high concentrations of expensive chemicals are necessary to obtain deinking and adequate pulp cleanliness is not achieved. Thus the present practice, employing known deinking processes require complex and expensive procedures to obtain recycled grade paper.
There is a need in the art for processes which are less complex to produce recycled paper. This invention is directed to the provision of such processes which have wide range applications in creating recycled paper with a high level of cleanliness, and using a low dosage of agglomeration chemical.
Accordingly, it is a broad object of the invention to provide a deinking process and related apparatus for the agglomeration of ink particles from wood containing and wood free grades of paper.
Another object of the invention is to provide a low cost agglomeration deinking process and apparatus that effectively and efficiently removes ink particles without using high concentrations of expensive agglomeration chemicals.
A still further object of the invention is to provide a recycled paper product having a high level of cleanliness made by the agglomeration deinking method of the invention from printed wastepaper.
A more specific object of the invention is to improve the yield of the agglomeration deinking process by reducing the amount of paper fiber which is rejected from the process system in the centrifugal cleaners.
Another object of the invention is to improve the removal of fine ink particles which normally must be removed in a washing process which entails substantial production of deinking sludge.
Another object of the invention is to increase the pulp brightness by removing the fine ink which reduces brightness, and thereby achieve a reduction in the requirement for expensive bleaching chemicals.